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FODMAPS – possibly the cause of your unhappy gut

FODMAPS might be a funny sounding acronym but bloating, cramping, constipation, diarrhea and pain are no laughing matter.


Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols is what the term stands for, essentially a group of undigested carbohydrates that produce gas after fermentation by gut bacteria leading to the irritable bowel like symptoms described above.

These foods, if undigested and malabsorbed, cause water to move into the small intestine resulting in diarrhea, or as they move into the large intestine they act as a food source for bacteria living there which, after fermentation, results in an increased amount of gas being produced and subsequently bloating, distension, flatulence, pain or constipation.

Oligosaccharide containing foods

Fructans in wheat, rye, onion, garlic
Galactans in legumes and pulses

Disaccharide containing foods

Lactose in milk, soft cheeses, yoghurt

Monosaccharide containing foods

Fructose in honey, some fruit, dried fruit and corn syrup

Polyol containing foods

Sugar alcohols (sorbitol, mannitol, xylitol etc) found in some fruit and artificial sweeteners

Whenever a client or patient presents with these chronic issues I screen for a diet that is high in these foods and try to eliminate them and then reassess. The improvements are often quite real and noticeable. These foods also suggest an alternative reason why anyone who has cut out wheat or dairy finds relief while not actually being allergic to these foods. Having a FODMAP intolerance is not an allergy and in the case of wheat it is not the gluten but the fructan content that is the issue.

Sensitivity to these foods and related symptoms can be brought on by a number of issues, including but not limited to

  • a naturally high FODMAP diet
  • bowel irregularities, blockages, constipation
  • digestive enzyme or stomach acid irregularities
  • damaged gut lining
  • excessive antibiotic use
  • bacterial overgrowth
  • lack of pre/probiotic containing foods
  • lactose or fructose malabsorption
  • overweight
  • stress
  • smoking
  • inactivity

If you struggle with these kinds of symptoms it may be worth trying an elimination diet and attempting to improve the bacterial health of your gut. An elimination diet should cut out all of these foods for 2-6 weeks while monitoring symptoms. You can look to include peppermint oil in the first couple weeks to assist with reducing symptoms and bacterial overgrowth. If small intestinal bacterial overgrowth (SIBO) is a concern then a short course of antibiotics can be discussed with your doctor after evaluation and diagnosis. SIBO is a related but separate disorder where bacteria which should be limited to the large intestine proliferates in the small intestine leading to similar symptoms. It is usually felt immediately after eating any food, not just these FODMAPS, and occurs much quicker. Regular sugar and fat are also usually poorly tolerated and there may be signs of fat malabsorption in foul smelling, oily stools.

This table is a nice basic introduction into the foods you should be looking to limit and alternatives for the 6 week period. I unfortunately came across this without knowing who to reference but the work is not my own.

I make use of a great app (available here as apple or android) when working with clients and patients. The app allows you to search for many foods and their FODMAP rating. It also provides guidance on portion control to keep your total fermentable intake down and offers a diary to keep track of your elimination diet. If this is something you are going to work through it is a valuable purchase.

gut health

After a 6 week elimination diet these fermentable carbohydrates should be reintroduced gradually to assess your individual tolerance. It is advised that the elimination and reintroduction is done in consultation with a dietician to avoid adverse risk and to ensure a balanced diet is maintained. It may be worthwhile to introduce a probiotic or at least some naturally fermented foods at this stage too in the form of pickles, tempeh or yoghurt depending on your tolerance.

You can fast track your guess-work by undergoing a breath test that will inform you on any fructose or lactose malabsorption issues. This test involves fasting, swallowing a sample of either lactose or fructose and then testing for the presence of hydrogen in your breath. If there is no sign on malabsoprtion then there is no need to avoid these particular foods and you can limit your exclusion to oligosaccharides and polyols only. A breath test can also be used to diagnose small intestinal bacterial overgrowth. The Sport Science Institute in Cape Town has previously offered breath testing so get in touch with them if necessary.

Your gradual reintroduction of foods should include one new food every 1-2 days with an assessment period of another 1-2 days. This would mean 2 new foods are reintroduced weekly while monitoring your symptoms. Choose the foods you have struggled cutting out or missed the most as your starting point.

A key element to following a low FODMAP diet is that there is also an apparent dose-response interaction. This means that you might be able to get away with eating all these foods after reintroduction provided that your total intake of FODMAP rich foods is still low. You should be able to learn fairly quickly how much of certain foods you can tolerate. Bare in mind that multiple foods in one meal will add to your FODMAP dose however.

If you have little or no benefit from adjusting these dietary components there may be something more to your concerns. Other lifestyle factors should not be ignored such as stress, weight, smoking or alcohol intake. Food allergies, such as gluten in celiac disease, have a low threshold and any amount will trigger a reaction. Obstructions or inflammation in the bowels may need to be ruled out too and so consulting with your doctor is necessary.

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